Recording system



May 24,-y 1960 RfA. PETERSON RECORDING SYSTEM 5 Sheets-Sheet 1 Filed D60. 19, 1955 G gi nrw ,HA yMo/vp .4. Pers/esa,

INVENTOR.

May 24, 1960 R. A. PETERSON 2,937,915

RECORDING SYSTEM Filed Dec. 19, 1955 5 Sheets-Sheet 2 1Q/z yMa/D .4. Perf-wsa,

INVENTOR.

rraeAv/Ey- May 24, 1960 R. A. PETERSON RECORDING SYSTEM 3 Sheets-Sheet 3 Filed Dec. 19, 1955 @www1 INVENTOR BY /rra/wey g'alvanom`eters, or'oscillographs, and'particularly to iml into corresponding electrical wave trains.

trical wave trains are then amplified electrically'and the .and all of the .wave trains are recorded relation asa multiple trace record.l Y 1 `Very commonly,'the excursions of neighboring'traces overlap, and obscure each other.' For this reason, when l.an attempt is made to measure the relative times of 'arrival 2,937,915 VvRECORDING sYsrEM Y A.Raymond A. Peterson, Altadena, Calif., assigner to United if Geophysical Corporation, Pasadena,A Calif., a corpora- 'tionoizCalifornaVV l K susana-19, 1955, ser. No. 554,041

7 claims. (ci. 346-109) invention relatesV to improvements in recording provements in multiple-galvanometers or oscillographs of i' the type employed in seismic prospecting and othertields Y in' which a plurality of traces representing closelyl related 'phenomenon are recordedin side-*by-side relationship on an elongated record strip;

Since the invention is particularly useful in reection Aseismic'y prospecting the application' of the invention 'to reection vseismic prospecting will"y be particularly described. However, it will be understood that the invention is'also applicable to refraction seismic prospecting methods Inrreection seismic` .prospectmg,y seismic waves are usually generated at a shotpoint near the surface of the earth hy detonating an explosive charge located in a shallow borehole. The wavesso generated are detected at a series of spaced seismometers located at the surface ofthe earth, after the waves have travelledV downwardly to variou'sformations and have been reflected upwardly vfrom the formations. In this process, a short Wave train v -or wavelet created at the time that the Vexplosive charge Vis detonated, is reflected bythe various subsurface .formaf v Ytions encountered as 4thewave travels downwardly. As

ra result, long trainsof seismic waves are returned to the lvarious seismometers at the surface of the earth. The

cause of differences existing between theA paths Yover which the wave trainsV travel to the various seismometers and for Vother reasons. y

y .The various trains of seismic waves reaching the different-seisrnometers are converted by the seismometers These elec- FCC the on and Gas Jamal, pp. 146 ff. Mr. John Widnes has described an improved method of plotting reilection Y proiile sections. This process,"which is ascribed to Mr. V. T. Reynolds, involves re-recording seismograph traces in such a way as to correct for normal moveout, weathering corrections, seismometer elevations, and horizontal variations in vertical velocity. In the Reynolds system, the usual paper seismogram is iirst reprintedas a transparency and then each trace of the reprint seismogram is printed by projection onto a separate recording sheet,

such as a large sheet of sensitized paper, in such away as to incorporate corrections for differences in elevation, for differences in weathering corrcctions,an d Yfor differences in step-out, makinguse of the velocity data that represents the manner in which seismic wavervelocity varies as a function of time of travel from'the shotpoint to formations atdiierent depths and then to the Aseismomandto othersystemsv in which records are made of a Y plurality ofy related measurements. c

l trains of waves usually bear a markedl similaritybut yet l f differ somewhat because of variations in subsurface formations from one horizontal position -to another and'beeters. Traces from other seismograms arc-.similarly refrecorded on the same large-sheet. By recording.; traces from different seismograms in side-by-siderrelationship and in lateral positions corresponding to the Vhorizontal positions of various parts of the subsurface from which waves on the seismograms were reilected, a vertical's'ection or prole of subsurface formations is produced. In the making of such plot itis often satisfactory to neglect the dip of the strata even4 though the 'existence of dip becomes self evident on the completed profile sectiom Another object of the invention is to provide aninradapted for use in a Reynolds plotter withoutY however,

phases of the ordinary`seismic wave tracer The foregoing and other objects of this inventionffto' discarding important information represented by different gether with various advantages thereof, will'becoxne ap .amplified wave'tr'ains are recorded by meansof amultiplegalvanoineter oscillograph.v In .this recording process, each electrical wave train is Yrecorded asia separate trace in side-by-side of seismic waves at dilerent seismometers,`it is diticult f toidentify related eventson dierent traces andn to accurately' measure their, relative timesof occurrence.A

Accordingly, one object of this'invention is to provide animproved multiple-element oscillograph in which each .electrical wave'train isrecorded as a'plurality of identical oscillograph traces, within the limits of 'adjacent non overlapping tracks of a record strip so :that overlapping of traces is avoided'but without loss of information 're'- Agarding the times of `occurrence of various recorded events. f

Y In an article entitled Better Seismic-Retiection Coinple-element oscillograph embodying' 'the'inventionl' with the accompanying drawings, wherein:` u

Figure 1 is a schematic diagram of apreectionfseismic prospecting system Vemploying this inven tion';",

Fig. 2 is a schematic diagram employed inexplaining' certain optical properties of the system; *1'

parent from the following descriptionrtakenfin connection Fig. 3 is a schematic diagram of an alternative form of source unit;

Figs. 4a and 4b varefdiagrams of alternative forms ot" screens that maybe v'en'iployed as part of the source unit; Fig. 5 represents a multiple trace oscillogram-prodnced by a single-elementoscillograph embodying thepresent invention; v l g Fig. 6 #represents a 'multiple-trace' seismogram prduced by the usual type of multiple-element oscillograph; .Fig.7' is a fragmentaryivi'ew of a .:nultiple-tracltnjlulti-y ple-trace seismogram produced in 'acfcorclaricel with "the present invention; and' 1 Y y ,y r Fig. '8 is aschematic cross-,sectional diagrmof ainixlti-V In accordance with this invention, duplicates'flan oscillographv trace are recorded in'vside5by-,sidefrieste'd relationship .on a common sheet of recording pper'orlm 'and certain duplicate traces arerecorded in a'distinctivei Pfsntsd. Mar 251%? traces may be readily recognized. When applying the invention to the recording of related events by means of a multiple-galvanometer oscillograph, each galvanometer of the ,oscillograph is arranged to produce its own set of `duplicate traces in side-hy-side relationship.' Furthermore, masking is provided to confine the recording of multiple traces from each recording element to a separate area or track on a common record sheet.v The tracks corresponding to the various oscillograph elements lie in side-b y-side relationship in, order to facilitateV correlation of events recorded on the separate tracks. The advantages of recording such duplicate traces can be best understood from the following description of a specific embodiment of the invention in the field of reflection seismic prospecting.

A system for recording a seismogram in accordance with this invention is shown in Fig. 1. This system includes a shothole h, a split spread of seismometers S1, S2, S3, S4, and S and associated amplifying and recording equipment, including the improved oscillograph C. Though the invention is described Ias being applicable to a split spread of tive seismometers, it will be understood that it is applicable to other types of seismometer spreads and to spreads comprising any number of seismometers such as twelve or twenty-four.

When a blaster B is manipulated, a charge of explosive E located in the shothole h generates seismic waves which travel outwardly in all directions. At the time that the blaster is operated an electric signal is transmitted to the oscillograph C in order to record a time break by means of one of the galvanometers. Seismic waves reflected at interfaces A between strata beneath the surface of the earth are returned to the surface where they are detected by means of the seismometers S1, S2, S3, S4, and S5. The seismometers are of conventional type which are adapted to convert the received seismic waves into corresponding .electrical waves. Such electrical waves vary as a function of time in a manner related to that in which the velocity of the surface of the earth varies as a function of time as the seismic waves are received. The electric waves generated at the outputs of the respective seismometers dier from each other because of the fact that the seismic waves received at the various seismometers differ from each other. In any system of seismic prospecting, it is desirable to record the electrical waves in some coordinated manner so that the relative times of occurrence of the various significant related events in the reected seismic waves may be ascertained, all as is well known in the art.

The outputs of the respective seismometers S1, S2, S3, S4, and S5 are connected to the inputs of corresponding amplifiers M1, M2, M3, M4, and M5. The amplified electrical waves appearing at the outputs of the respective amplifiers M1, M2, M3, M4, and M5 are applied to corresponding galvanometers G1, G2, G3, G4, and G5. At various points in the description that follows subscripts will be omitted when the description applies equally to similar elements. Thus, for example, when the description applies equally to any of the galvanometers G1, G2, G3, G4, or G5, the symbol G will be used without any subscript.

As indicated more clearly in Fig. 2, each of the galvanometers G comprises a coil W wound on a pair of bobbins b and pivotally supported torsionally by means of two collinear torsion wires w, w, the upper and lower most ends of which are rigidly supported in stationary insulating bushings u, u. A galvanometer element in the form of a cylindrical mirror I is cemented to the lower wire w. The windings W1, W2, W3, W4, and W5 of the various galvanometers G1, G2, G3, G4, and G5 are arranged in a. common linear gap g between the north and the south poles of a permanent magnet Z. The various mirrors I1, I2, I3, I4, and I5 of the respective galvanometers G1, G3, G3, G4, and G5 are arranged along a line exterior of the gap in which the coils W1, W3, W3, W4, and W5 are mounted and on the opposite side of `that gap from the main body of the permanent magnet E. The various wires w by means of which the windings W and the mirrors I are suspended are arranged in a common plane in parallel lines that lie perpendicular to the length of the magnet gap.

In this embodiment of the invention, a multiple-element source unit SU is employed in order that each of the galvanometer mirrors I shall produce a plurality of identical or duplicate oscillograph traces. Light is projected from a plurality of sources in the source unit SU along a central optic axis X-X-X that intersects each mirror I to the plane of a sheet of photographic paper P forming a line of spots of light in the plane of the recording sheet P. The spots of light produced by each mirror I are displaced along a rst or horizontal direction as the recording paper P is advanced in a second or vertical direction transverse to the optic axis. As a result, multipletrace records are produced by each mirror in side-by-side relationship on the recording paper P.

The source unit SU, in effect, consists of a plurality of vertically extending sources of light U1, U2, U3, U4, U5 arranged in side-by-side parallel relationship along a horizontal line. In the specific source unit illustrated, the sources are in the form of narrow slits formed in a screen N and a lamp Q having a horizontally disposed filament F. The filament serves as a horizontal light source which illuminates the various slits U1, U2, U3, U4, U5. In the most satisfactory arrangement, a cylindrical lens L1 having a horizontal axis is located between the lamp Q and the screen N. The lens L1 focuses in a vertical plane an image of the filament F on the various slits U1, U2, U3,.U4, U5 along a common horizontal line extending through the central optic axes X-X-X. A

' cylindrical lens L2'having a vertical axis may be employed between the lamp Q and the rst cylindrical lens L1 in order to focus light from the Ifilament F at the screen N in a horizontal direction, as indicated in Fig. 3, and in this case the elongated real image at the screen acts as a real source in the plane of the screen. It is not essential that such an image be formed in a horizontal plane at the screen N, it being beneficial to employ the cylindrical lens L1 to focus at the screen N in a vertical plane light emerging Vfrom the filament F, so as to elect ecient transmission of radiation to the recording paper l. Furthermore, where desired, the lenses L1 and L2 may be combined to form a single spherical lens. In addition, a eld lens F may be mounted adjacent the screen N and on the side thereof remote from the galvanometer mirrors I. This field lens is employed to cause light passing through Athe slits to converge on the line of mirrors I, thus serving to increase the intensity of and the uniformity of intensity of the spots S formed by each mirror I at the plane of the recording paper P.

Each ofthe mirrors I is provided with a front cylindrical surface having a vertical axis for focusing in a horizontal plane each of the vertical slits U1, U2, U3, U4, U5 at the plane of the recording paper P. A cylindrical lens L3 having a horizontal axis is located adjacent the plane of the recording paper P. This lens has a short focal length so that it focuses in a vertical plane images of portions of the lament as seen through the respective slits U1, U2, U3, U4, U5. The images formed atthe photographic'paperare highly minied vertically. Thus, each of the cylindrical mirrors I and the horizontal lens L3 cooperate to form a plurality of images in the form of small spots s', s", sf", si", and sv at the plane of the recording paper P, each spot so formed corresponding to a different slit U1 U5.

The distance of the recording paper from each of the mirrors I is about equal tothe distance of each of the mirrorsfrom the screen N, so that a magnification of about one is produced in a horizontal plane. On the other hand, the cylindrical lens L3 is very close to the recording paper, thus producing a very high degree of A lchannelizer H is arranged aes-71191# mrlsation; ,Such as ,a minicationpf 1,00. in .a Yertsl plane.l Thus', even if the varioussourceelements U1, U2, Us, U4, U are elegonatedjinga vertical plane and radia- ,tion passes'through therri over air-extended verticalregion, Yeachof themirrors land th`e' horizontal lens L3 cooperateA to form imageseofthe source units in the form of very smallAspots lat thev plane o f the recording paper. f Such miniication occursV in a vertical plane even if 'the ,source Qis not focused in a vertical plane at the screen N. B ut for best results, the source Q itself or else its image e in a vertical plane is focused by the lensL3 in a vertical f plane at the-plane of the recording paperV P. .The spots formed by all five mirrorsV lie Von. aA common horizontal line in a horiozntally elongated exposure or recording zone ,behind theY lens L3 at the plane of the recording Y paperiP.'l The sources U1, U2, Us, IIb-,Usare formed by indi'- vidualv vertical transparent ,s'litsinl an opaque scr'e'en N.

The screen may be in the form ofV a photographic plate orY a sheet of photographic film which is coated with opaque' portions 'except `at thelocations ofthe slits. Y The slits 'n'eed notall have"th`ersame` width. Furthermore, they needV not be five in, number. A'screen N provided with -nineteen slits is illustrated in4 Fig. 4a. In this case, the central'slit is Ywider than the rest and the other slits are of uniformnwidth. With this arrangement, the central spot focused vonthe recording paper is wider than rthe other spots,thus .exposing ,the photographic paper more.

Thus,`images.ofrthe respectivey slits U are focused as spots si at the .plane of the sheet of recording paper P.

Asjeachrnirror I rotates about Vits vvertical, axis, the spots j s g'. sv produced thereby at`the plane of the recording paper move horizontally in unisonl and ",by substantially; equal amounts-, For this reason, as a trainV of relectrical waves applied to anyfgalvanometer recorded,. a pluraliy 'of duplicate or' identicalv traces are recorded onthe recordingpaper in nested side-by-side relationship. I'

. specimen vof such ka set f traces produced with a .nineteen-slit screen N, is illustrated in Fig. 5. This set of traces comprises a central dark trace To with nine light traces TY disposed at uniformdistances on each side of the centraldark trace. Such a set of duplicate traces y producedwheny the screen N comprising the multipleyelement source is provided witharelatively broad Vertical slit at {thecenterandnine relatively narrow slits on each sfide thereof, as 'illustrated `in' Fig. 4a. In a similar Y manner, in the examples illustrated-in Figs. 1 and 2, a

`centralV dark trace To' isv formed'by each galvanorneter mirror 'and two light tracesT are formed on opposite sides thereof. Other arrangements of slits may be employed.ln Fig. 4b, for example, a screen is illustrated whichis formed by ten evenly ,spaced transparent. lines and tenjevenly spaced opaque lines arrangedl symmetrically ali'out'thecenter.` Y

y l lbetween the set of galvanor'neter mirrors I and the recording paper P ink order to, coniine the traces produced by each mirror Ito a separate Vtra"ck, and thusY prevent overlapping. The

Ichanneli'zer H comprises a set of vertical separator plates for wall ,membersVv that -are. spaced apart ,horizontally andare 'locatedrbetween the parts of the central optic axes XX-Xfalong which thev respective galvanonieter mirrorsfI` projectbeams'toward the recording paper R.

'When iiyefgalvanometers are employed, six such separator plates vY are used, thereby providing iive channels through which the .opticv axes X-X-X of the con-esponding mirrors M extend. Masksv are arranged at the e, ,ends` of Vthe channels adjacent the recording paper 1R.

These masks limit the area Vthroughwhichlight from Y I. therespectivemirrors may be projected onto the recordi11 g p 'aperfthus,dividing therecording paper intoiive i liorizontaltraeks between the side'sof which the multiple ltracesproducedby each mirrorvare confined. The separa'tor'platY prevent light'from any mirrorfrom passing through, any maskother than the one thatcorresponds to it. "way, 'overlapping of traces is completely avoided'.

A part of a multiple track record produced in ajccord-V ance with this invention is illustrated in Fig. 7. There, .a

it will be noted that each track K1, K2, K3, K4,KK5 occupies a separate elongated .area or strip on the record? ing paper R and that multiple traces produced by each mirror M1, M2, M3, M1, M5 are recorded in the separate tracks. However, it will benoted that the limitation of the widths of the tracks results in truncation or clipping of many of the traces. Referring to Fig. 7, itV will be noted that the central dark trace produced by` each mirror is displaced from side to side in accordance ywithv the deflection of the mirror, but that generally it can readily be identied. Furthermore, it will be noted that even though some of the traces infeach track are truncated,

normally a-complete set ofrepresentative partsof veach set of traces are recorded in each of the tracksJ For this reason, .it is possible to locate in each` track both a positivey peak ppand a negative peak np. The location and identiicationofsuch peaks is employed in seismic prospecting tQ-determne'the'reIatVe tiniesof arrival of seismic waves at various seismometers after the waves are reectedfrom common reflecting horizons beneath A the surface of the earth.` In Fig. 6 there is illustrated a seismogramof the` ordinary type produced when each mirror produces only a single spot at Vthe krecording paper and no 4channelizerv isemployed. Herreit will be noted that the excursions of the traces overlaprsomewhat. The widths of the various tracks K1, K2, K3, K4, K5 are all equal, and are greater-than the spacing between adja cent duplicate tracesV to', be recorded. Thewidths'of the tracks K1, K2, K3,K4, K5 are also less than the amplitude of the excursionsof the spots thatproduce the traces. v

In this way,- as a rule, the tracks will be Voccupiedby a plurality of parallel evenly spaced traces. Occasionally, however, as indicatedffor instance, at the points d of Fig. 7, the excursions of the spots will be excessive 'leaving some blanks spaces in the tracks. This Yobjection may be overcomeby employing a wider source'unit SU. g

To Vrecord the time break, an electrical signal from the blaster B is applied to one of the :galvanometers G through a switching circuit (not shown).` f-

In the ordinary multiple-element oscillograph, suitable means are provided for recording timing' lines that extend across the entirewidth of the recording paper. .Such timing lines t produced by conventionalmethods are indicated in Fig. n6., `In the present inventiongonly segments of tim'ing lines are recorded, these segments being recorded in separate timing line tracks YKTlaud KTZ., i

adjacent opposite edgesofA the recording paper externally of but parallel to the tracks K1, K2,K3, K4, K5 in which the various sets of traces are recorded; As indicated schematically in Fig. 1, such sets of timing linesV drum onto the recording paper P. This light is projected through end sections of the cylindrical `le'nsrLg, so

as to produce thin timing linesl in the'tracksKTl and j 1 Y KTZ at the sides of the record paper. The'mirrors Y; Y

preferably have spherical surfaces focusing an image "of Y the cylindrical lens La at the cylindrical lens La. KSuit- Y able masks mt limit the width of the beamsto the'timingtracks KTI and KTZ. It is to be noted that Vsiriceathe drum is located off the optic axis X-X-X, even 'though l Some light frmthe drum Strike fhesalvwm'e.

per mijn rors I1, I2, I3, I4, I5, very little `of this light-can be transmitted from the galvanometer mirrors to the recording paper. Other masks are provided-to -prevent light 'from travelling from the drum to the recording paper except along th paths desired. Details of such masking arrangements are not shown because they can be readily provided by a man having ordinary skill in the art.

In practice, the traces produced directly on the recording paper by projection of light from the galvanometer mirrors I and Y form latent images, which are subsequently developed by the usual chemical processes, thus producing visible traces as illustrated in Fig. 7.

A driving mechanism of any conventional form may be employed to drive the recording paper P past the images or spots formed at the plane of the recording paper by the cylindrical lens L3.' Such a driving mechanism may include, for example, a motor-driven roller 20 which draws paper oi of a supply spool 22 forcing it past the lens L3 at constant speed and into a storage can 24.

In this arrangement the source unit SU is arranged at a top corner of thevhousing and the magnet Z and galvanometers G at a corner directly beneath it. Light from the source unit SU is rellected by the galvanometer mirrors I to an auxiliary mirror 26 that reects the light upwardly through the channelizer H and through the lens L3 onto a part of the recording paper being carried over the roller 20. The/timer is arranged at the center of the housing and the mirrors Y are mounted adjacent the channelizer so that both the timing lines and the spots formed by the galvanometer mirrors may be brought to a sharp focus on the recording paper even though the latter is curved in the recording zone. Suitable switches (not shown) are employed for driving and stopping the recording paper when desired.

By providing the drum D with ten slits, nine of which are relatively narrow and of equal width, and one of which is relatively broad, every tenth timing line on the two tracks KT1 and KTZ is made dark compared with the others as indicated in Fig. 7.

In addition to the foregoing, the oscillograph of this invention employs a suitable light-tight case for housing the galvanometers, the record drive mechanism, the source unit U, the timer drum, and the channelizer as indicated for example in Fig. 8. Y

When the invention is applied to the recording of only a single track by means of a single galvanometer mirror to vproduce a single multiple-trace record as indicated in Fig. 5, its use is advantageous because it provides an improved visual representation of variations in the phenomenon recorded. When the invention is applied to a multiple-track system in a multiple galvanometer recording oscillograph to produce a multiple track record as illustrated in Fig. 7, it has even greater advantage. In the case of a multiple track record, the correlation of corresponding events in the differentV tracks by visual means is greatly enhanced. This improvement in visual correlation results largely from the apparent shading which occurs in the recording process during the recording of the changes. This variation of shading along the length of track occurs because of the fact that as the light spots that produce the records are moved horizontally, a variation occurs in the spacing between the duplicate traces produced. As a result, a pattern appears on the record which facilitates identification of corresponding changes on the various tracks. Once corresponding events on the various tracks have been identitied, the relative times of occurrence may be determined from the relative locations of peaks in the various tracks along the length of the record. Such locations may be measured accurately by means of the timing lines in the edge tracks KT1 and KTZ, thus determining the relative `times of occurrence of the related events. The manner in which such differencetime measurements'may be employed in the anlysis of assiste seismic reection records is Well known in the art and therefore is not discussed here.

In addition to the foregoing,` it will be noted that if a multiple-track recordof the type illustrated in Fig. 7 is employed to produce Va prole section by means of a Reynolds or similar plotter, the variations in shading characteristic of the traces recorded in each track K will be reproduced fairly closely on the prolesection. As a result, this grading or shading from one position to another along the Reynolds profile section will have the general appearance of stratified layers and will therefore assist the interpreter in recognizing changes in elevation, changes in thickness, faulting, and other changes occurring in the subsurface structure in the area in which the original reflection seismograph prospecting survey was made. Y

In the specific embodiment of the invention described above, the multiple-track seismogram of this invention has been recorded on photographic paper. In an alterna` tive embodiment of the invention, the seismogram is recorded directly on film. This arrangement has the advantage that it provides a seismogram that may be replotted by projection methods in a Reynolds or similar plotter without the need for rst reprinting the paper seismogram on transparent lm. Advantageous use of lthis principle may also be made to produce single-trace multipletrack seismograms. To do this, it is only necessary to construct the screen N in the form of a single opaque line on a transparent plate. In that case, seismograms will be produced like those illustrated in Fig. 7V except that a single truncated transparent trace will appear in each track which is otherwise opaque. l

While the invention has been described with particular reference Ato its application to reflection seismic prospecting, it will be understood that it may be applied to other systems in which similar related events occurring simultaneously or even at different times are recorded by means of a galvanometer. It is therefore to be understood that the invention is not limited to the speciiic applicationthereof described herein, but that it may be employed in many other ways, as will now appear to those skilled in the art. Furthermore, even though the invention has beenV described with reference to only one particular arrangement for producing a plurality of duplicate traces representative of a single variable signal, it will be understood that such duplicate traces may also be produced in other ways. Itis therefore to be understood that the invention may be used in many other ways and may be embodied in many other forms Within the scope of the appended, claims.

The invention claimed is:

l. In a multiple element oscillograph in which a strip of recording material is moved in a longitudinal direction past a recording line means including, a multiple light source unit and a plurality of light-deilecting galvanometer elements for projecting light from said source unit to said recording line along aset of neighboring paths, whereby a set of spots of light are produced at said recording line by said each galvanometer element, each said set of spots of light moving in unison transverse to said longitudinal direction as said each galvanometer element is detlected, the spacinggbetween the spots of each set being small compared with the spacing between said neighboring paths, and a masking means for confining the projection of light by each galvanometer element to a separate track on said recording strip whereby each galvanometer element produces a plurality of parallel nested oscillographic traces representative of the same signal only within the limits of a corresponding track on said recording strip.

2. yIn Va multiple element oscillograph in which a strip of recording material is moved in a longitudinal direction past a recording line, means including a multiple light source unit and a plurality of light-deecting galvanometer elements arranged in side-by-side relationship for cording line by said each ygalvanometer element, the light spots of each said set moving in unison transverse to said longitudinal direction as said each galvanometer element is delected, the spacing between the spots of each set l being small compared with the spacing between said neighboring paths, and channelizing means including wall members located between saidgalvanometer elements and said Irecording line for confining the projection of light by each galvanometer element to a separate track on said recording strip whereby each galvanometer element produces a plurality of parallel nested oscillographic traces representative of the same signal only within the limits of a corresponding track on said recording strip.

3. In a multiple element oscillograph in which a strip of recording material is moved in a longitudinal direction past a recording line, means including a multiple light source unit -and a plurality of light-deilecting galvanometer elements arrange in side-by-side relationship for projecting light from said source unit to said recording line along a separate set of neighboring coplanar paths, whereby a set of spots of light lare produced at said recording line by said each galvanometer element, the light l spots of each said set moving in unison transverse to said y by each galvanometer element produces a plurality of parallel nested oscillographic traces representative of the same signal only within the limits of a corresponding track on said recording strip.

4. In a multiple element oscillograph in which a strip of recording material is moved in a longitudinal direction past a recording zone, a plurality of light sources arranged at a source position `along aline transverse to said longitudinal direction, a plurality of galvanometer mirrors for reilecting light from said sources to said recording zone, each of said galvanometer mirrors being adapted to project light from said sources to said recording zone along a separate set of neighboring paths, whereby a set said each galvanometer mirror, the light spots of each Ilo said set moving in unison transverse to said longitudinal direction when said each galvanometer mirror is deected, the spacing between Ithe spots of each set being'small compared with the spacing between said neighboring paths, Y

and channelizing means including wall members located between said galvanometer mirrors and said recording zone and masking means located at the end of vsaid channelizing means near said recording zone for confining the projection of light by each galvanometer mirror toa separate track on said recording strip whereby each galvanometer mirror produces a plurality of parallel nested oscillognaphic traces representative of the same signal only within the limits of a corresponding track on said recording strip.

5. A recording oscillograph as defned'in claim 4 in which said light sources are formed by a device having a plurality of slits arranged with their lengths transverse to said recording zone and spaced apart in the direction of said recording zone, together with means for projecting light through said slits toward said galvanometer mirrors.

6. A recording oscillograph as defined in claim 4 wherein said light sources are formed by a linear light emitting element extending transverse to said longitudinal direction and a screen disposed between said linear light emitting element and said mirrors and having a plurality of mutually spaced apertures therein disposed along a line transverse to said longitudinal line. A

7. A recording oscillograph as dened in claim 6 in which said apertures are in the form of parallel slits disposed parallel to said longitudinal direction and comprising a cylindrical lens disposed between said linear light emitting element and said screen for causing light diverging from said linear light emitting element to converge on said screen.

References Cited in the iile of this patent UNITED STATES PATENTS 

